Current Electricity

A wire of resistance 20 is divided into 10 equal parts. A combination of two parts are connected in parallel and so on. Now resulting pairs of parallel combination are connected in series. The equivalent resistance of final combination is .

The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are 8 and 10 respectively. After inserting in a hot bath of temperature 400 , the resistance of platinum wire is :

1. 10
2. 16
3. 8
4. 2

To measure the internal resistance of a battery, potentiometer is used. For R=10 , the balance point is observed at l=500 cm and for R=1 the balance point is observed at l=400 cm. The internal resistance of the battery is approximately :

1. 0.1
2. 0.3
3. 0.2
4. 0.4

Twelve wires each having resistance 2 are joined to form a cube. A battery of 6 V emf is joined across points a and c. The voltage difference between e and f is V. [figure]

An electric bulb rated 50 W–200 V is connected across a 100 V supply. The power dissipation of the bulb is:

1. 100 W
2. 50 W
3. 12.5 W
4. 25 W

Two wires A and B are made up of the same material and have the same mass. Wire A has radius of 2.0 mm and wire B has radius of 4.0 mm. The resistance of wire B is 2 . The resistance of wire A is .

The reading in the ideal voltmeter (V) shown in the given circuit diagram is : [figure]

1. 3 V
2. 10 V
3. 5 V
4. 0 V

The current in a conductor is expressed as I = 3t2 + 4t3, where I is in Ampere and t is in second. The amount of electric charge that flows through a section of the conductor during t = 1 s to t = 2 s is C.

In a metre-bridge when a resistance in the left gap is 2 and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 , the balance length changes by :

1. 62.5 cm
2. 22.5 cm
3. 20 cm
4. 65 cm

To measure the temperature coefficient of resistivity of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor. The experiment is being conducted at 25 and resistance of the semiconductor arm is 3 m . Arm BC is cooled at a constant rate of 2 /s. If the galvanometer G shows no deflection after 10 s, then is : [figure]

1. -1 10-2 C-1
2. -2 10-2 C-1
3. -2.5 10-2 C-1
4. -1.5 10-2 C-1